Remove balloon notification code. The last user was the Linux GTK port but that's deleted now.

chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/message_center/web_notification_tray.h"
 
 #include <set>
 
 #include "ash/root_window_controller.h"
 #include "ash/system/status_area_widget.h"
@@ skipping 189 matching lines @@
   EXPECT_TRUE(tray->message_center_tray_->popups_visible());
   EXPECT_EQ(notifications_to_add, message_center->NotificationCount());
   NotificationList::PopupNotifications popups =
       message_center->GetPopupNotifications();
   EXPECT_EQ(kMaxVisiblePopupNotifications, popups.size());
 }
 
 IN_PROC_BROWSER_TEST_F(WebNotificationTrayTest,
                        ManuallyCloseMessageCenter) {
   NotificationUIManager* manager = g_browser_process->notification_ui_manager();
-  ASSERT_TRUE(manager->DelegatesToMessageCenter());
   MessageCenterNotificationManager* mc_manager =
       static_cast<MessageCenterNotificationManager*>(manager);
 
   WebNotificationTray* tray =
       static_cast<WebNotificationTray*>(mc_manager->tray_.get());
   ASSERT_TRUE(NULL != tray);
 
   message_center::MessageCenter* message_center = tray->message_center();
 
   bool shown = tray->message_center_tray_->ShowMessageCenterBubble();
   EXPECT_TRUE(shown);
   EXPECT_TRUE(message_center->IsMessageCenterVisible());
 
   mc_manager->EnsureMessageCenterClosed();
 
   EXPECT_FALSE(message_center->IsMessageCenterVisible());
   if (NULL != tray->message_center_delegate_)
     EXPECT_TRUE(tray->message_center_delegate_->GetWidget()->IsClosed());
 }
 
 }  // namespace message_center